The government is being urged to set up an early warning system for chemical or plastic spills in Hong Kong waters as even more pellets piled up on beaches yesterday.

But the environment minister defended the government's response to the tonnes of plastic pellets from a container ship that washed ashore at 10 beaches.

Secretary for the Environment Wong Kam-sing said half of the 150 tonnes of pellets that were lost from the ship during Typhoon Vicente on July 23 have been recovered. More than 200 volunteers showed up at Nim Shue Wan in Discovery Bay for a third day yesterday to help with the collection and cleanup.

DB Green called for volunteers after alerting residents on its website last month about the "massive spill" that washed up about 750 kilograms of plastic pellets at Sam Pak Wan in Discovery Bay.

"This equates to at least 30 million individual pieces of plastic, which has far-reaching implications," said Kate Wade on the website.

But Wong, who was speaking yesterday for the first time about the spill as he visited Nim Shue Wan, insisted that "prompt action" had been taken. As the plastic pellets are "not toxic," water quality has not been affected, he added.

A trace amount of plastic pellets was found at Ma Wan and Cheung Sha Wan fish culture zones yesterday but no "abnormal activity or death of fish" have been reported, said Assistant Director of Agriculture, Fisheries and Conservation So Ping-man, who was with Wong.

Islands District Council member

(Discovery Bay) Amy Yung Wing- sheung, who was also at the cleanup, said: "The government should have alerted the green groups and the local community at the earliest possible time about the spill.

"All these pellets have now been washed ashore at other beaches."

She will have the pellets tested and will take up the issue at the district council meeting later this month to urge the government to take prompt action in future and to determine who is responsible for the spill and any delays in informing the government.

Separately, Secretary for Food and Health Ko Wing-man said the plastic pellets are not toxic chemicals and that the Centre for Food Safety will closely monitor fish sold in the market.